Clinical applications of reinforcement-based treatments for problem behavior in persons with intellectual and developmental disabilities reduce the frequency of problem behavior by reinforcing an explicit desirable alternative (DRA), making reinforcers contingent on the absence of problem behavior (DRO), or providing reinforcers independently of responding (NCR). Although these methods can be highly effective in reducing the frequency of problem behavior to low levels within the treatment context, they can also have the perverse effect of increasing the persistence of problem behavior if some aspect of the context is altered or if lapses in treatment integrity occur. This clinically problematic outcome is predicted by behavioral momentum theory, which proposes that the frequency and persistence of behavior are separately determined by response-reinforcer contingencies such as DRA, DRO, or NCR, and by the overall rate of reinforcers obtained in the setting (which is increased by presenting alternative reinforcers according to any contingency). This project will evaluate the extent to which different contingencies for presenting alternative reinforcers (Specific Aim 1) and the rate of alternative reinforcers (Specific Aim 2) contribute to the persistence of problem behavior. In addition, it will develop methods that may reduce the persistence of problem behavior by arranging that desirable alternative behavior is reinforced in a separate setting, elements of which may then be brought into the treatment setting to reduce the frequency of problem behavior (Specific Aim 3), or by making access to that separate setting contingent on the absence of problem behavior (Specific Aim 4). Studies addressing each of these aims will be conducted with animal subjects in controlled experimental conditions modeled on those in which basic research on behavioral momentum originated. These studies will be repeated with children with intellectual and developmental disabilities in translational settings employing arbitrary responses analogous to problem and alternative behavior to ensure applicability of the animal data to the clinical population. Clinical interventions addressing significant problem behavior in children with intellectual and developmental disabilities will apply the most effective methods identified in basic and translational studies. Coordination of these studies within a single research project and the integration of their findings across the full range from basic research to clinical application will contribute importantly to effective treatment.